Method and device for low-complexity multiple-input multiple-output orthogonal frequency division multiplexing channel equalization

Abstract

According to an embodiment, a method of an electronic device for receiving a signal in an OFDM system may comprise an operation of determining a common channel estimation value on the basis of demodulation reference signals belonging to a resource block including a plurality of OFDM symbols adjacent in the time domain and a plurality of subcarriers adjacent in the frequency domain. The method of the electronic device may comprise an operation of determining a port reduction filter for reducing the dimension of a reception signal on the basis of the common channel estimation value. The method of the electronic device may comprise an operation of determining a covariance matrix on the basis of a reception signal having passed through the port reduction filter. The method of the electronic device may comprise an operation of performing channel equalization on the basis of the port reduction filter and the covariance matrix.

Description

Method and device for low-complexity multiple-input multiple-output orthogonal frequency division multiplexing channel equalization

[0001] The present disclosure relates to a receiver and receiving technology for a multiple input / output system utilizing orthogonal frequency division multiplexing or orthogonal frequency division multiple access.

[0002] Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) communication systems can dramatically increase the transmission speed and stability of wireless communications, and are utilized as core technologies for various wireless communication systems. To achieve high transmission speeds and stability in MIMO-OFDM systems, accurate channel estimation and channel equalization at the receiver are essential. A representative method for channel estimation is to utilize a demodulation reference signal (DM-RS) assigned to a specific resource element. However, methods using DM-RS can experience significant degradation in channel estimation performance in weak electric field environments where noise or inter-cell interference signals are strong. Furthermore, methods using DM-RS can also significantly degrade the performance of channel equalization based on the estimated channel if a channel estimation error occurs.

[0003] To overcome the performance degradation of channel estimation and equalization in weak-field environments, various iterative channel and data estimation techniques have been proposed. However, all iterative techniques require high computational complexity, which increases as the number of MIMO-OFDM antennas increases. Therefore, iterative techniques may not be suitable for MIMO-OFDM systems utilizing a large number of antennas. There is a need to develop low-complexity receiving methods and devices capable of performing channel equalization in weak-field environments with low complexity and robustness to channel estimation errors.

[0004] The above information may be provided as background information to aid in understanding this document. None of the above is claimed to be prior art related to this document or can be used to determine prior art.

[0005] The present disclosure relates to a multiple-input multiple-output (MIMO) system based on orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA).

[0006] According to one embodiment, a method of an electronic device for receiving a signal in an orthogonal frequency division multiplexing (OFDM) system may include an operation of determining a common channel estimate based on demodulation reference signals belonging to a resource block comprised of a plurality of adjacent OFDM symbols in a time domain and a plurality of adjacent subcarriers in a frequency domain. The method of the electronic device may include an operation of determining a port reduction filter for reducing a dimension of a received signal based on the common channel estimate. The method of the electronic device may include an operation of determining a covariance matrix based on a received signal that has passed through the port reduction filter. The method of the electronic device may include an operation of performing channel equalization based on the port reduction filter and the covariance matrix.

[0007] According to one embodiment, a storage medium storing at least one computer-readable instruction, wherein the at least one instruction, when executed by at least a part of at least one processor of an electronic device, causes the electronic device to perform at least one operation. The at least one operation may include determining a common channel estimate based on demodulation reference signals belonging to a resource block comprised of a plurality of adjacent OFDM symbols in a time domain and a plurality of adjacent subcarriers in a frequency domain. The at least one operation may include determining a port reduction filter for reducing a dimensionality of a received signal based on the common channel estimate. The at least one operation may include determining a covariance matrix based on a received signal that has passed through the port reduction filter. The at least one operation may include performing channel equalization based on the port reduction filter and the covariance matrix.

[0008] According to one embodiment, an electronic device may include at least one processor; and a memory storing at least one instruction. The at least one instruction, when executed by at least a portion of the at least one processor, may cause the electronic device to perform at least one operation. The at least one operation may include determining a common channel estimate based on demodulation reference signals belonging to a resource block comprised of a plurality of adjacent OFDM symbols in the time domain and a plurality of adjacent subcarriers in the frequency domain. The at least one operation may include determining a port reduction filter for reducing a dimension of a received signal based on the common channel estimate. The at least one operation may include determining a covariance matrix based on a received signal passing through the port reduction filter. The at least one operation may include performing channel equalization based on the port reduction filter and the covariance matrix.

[0009] The method and device according to the embodiment of the present disclosure can improve the reception performance of a multiple input multiple output (MIMO) system.

[0010] In connection with the description of the drawings, the same or similar reference numerals may be used for the same or similar components.

[0011] FIG. 1 is a block diagram of an electronic device within a network environment according to one embodiment of the present disclosure.

[0012] FIG. 2A is a block diagram of an electronic device for supporting legacy network communication and 5G network communication according to one embodiment of the present disclosure.

[0013] FIG. 2b is a block diagram of an electronic device for supporting legacy network communication and 5G network communication according to one embodiment of the present disclosure.

[0014] FIG. 2c is a block diagram of an electronic device for supporting legacy network communication and 5G network communication according to one embodiment of the present disclosure.

[0015] FIG. 3 is a diagram illustrating the concept of a resource block, which is the minimum unit to which a receiving method according to one embodiment of the present disclosure is applied.

[0016] FIG. 4 is a diagram showing an example of a basic unit of time and frequency resources constituting a downlink control channel according to one embodiment of the present disclosure.

[0017] FIG. 5 is a diagram illustrating an example of a configuration for a downlink RB structure according to one embodiment of the present disclosure.

[0018] FIG. 6A is a diagram illustrating an example of a DL MU-MIMO environment in a wireless communication system according to one embodiment of the present disclosure.

[0019] FIG. 6b is a diagram illustrating an example of a DL SU-MIMO environment in a wireless communication system according to one embodiment of the present disclosure.

[0020] FIG. 7 is a block diagram showing in detail the process of executing a receiving method of a MIMO-OFDM communication system according to one embodiment of the present disclosure.

[0021] FIG. 8 is a diagram illustrating a receiver structure of a MIMO-OFDM communication system according to one embodiment of the present disclosure.

[0022] FIG. 9 is a flowchart showing the overall operation process of a receiving method according to one embodiment of the present disclosure.

[0023] FIG. 10 is a diagram showing an example of a frame error rate versus signal-to-noise ratio that various receiving methods according to one embodiment of the present disclosure can achieve.

[0024] FIG. 11 is a diagram illustrating another example of a frame error rate versus signal-to-noise ratio that various receiving methods according to one embodiment of the present disclosure can achieve.

[0025] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein. In connection with the description of the drawings, the same or similar reference numerals may be used for identical or similar components. Furthermore, in the drawings and related descriptions, descriptions of well-known functions and configurations may be omitted for clarity and conciseness.

[0026] FIG. 1 is a block diagram of an electronic device (101) within a network environment (100) according to various embodiments. Referring to FIG. 1, in the network environment (100), the electronic device (101) may communicate with the electronic device (102) via a first network (198) (e.g., a short-range wireless communication network), or may communicate with at least one of the electronic device (104) or the server (108) via a second network (199) (e.g., a long-range wireless communication network). In one embodiment, the electronic device (101) may communicate with the electronic device (104) via the server (108). According to one embodiment, the electronic device (101) may include a processor (120), a memory (130), an input module (150), an audio output module (155), a display module (160), an audio module (170), a sensor module (176), an interface (177), a connection terminal (178), a haptic module (179), a camera module (180), a power management module (188), a battery (189), a communication module (190), a subscriber identification module (196), or an antenna module (197). In some embodiments, the electronic device (101) may omit at least one of these components (e.g., the connection terminal (178)), or may have one or more other components added. In some embodiments, some of these components (e.g., the sensor module (176), the camera module (180), or the antenna module (197)) may be integrated into one component (e.g., the display module (160)).

[0027] The processor (120) may, for example, execute software (e.g., a program (140)) to control at least one other component (e.g., a hardware or software component) of the electronic device (101) connected to the processor (120) and perform various data processing or operations. According to one embodiment, as at least a part of the data processing or operations, the processor (120) may store commands or data received from other components (e.g., a sensor module (176) or a communication module (190)) in a volatile memory (132), process the commands or data stored in the volatile memory (132), and store result data in a non-volatile memory (134). According to one embodiment, the processor (120) may include a main processor (121) (e.g., a central processing unit or an application processor) or an auxiliary processor (123) (e.g., a graphics processing unit, a neural processing unit (NPU), an image signal processor, a sensor hub processor, or a communication processor) that can operate independently or together with the main processor (121). For example, when the electronic device (101) includes the main processor (121) and the auxiliary processor (123), the auxiliary processor (123) may be configured to use less power than the main processor (121) or to be specialized for a given function. The auxiliary processor (123) may be implemented separately from the main processor (121) or as a part thereof.

[0028] The auxiliary processor (123) may control at least a portion of functions or states associated with at least one component (e.g., a display module (160), a sensor module (176), or a communication module (190)) of the electronic device (101), for example, on behalf of the main processor (121) while the main processor (121) is in an inactive (e.g., sleep) state, or together with the main processor (121) while the main processor (121) is in an active (e.g., application execution) state. In one embodiment, the auxiliary processor (123) (e.g., an image signal processor or a communication processor) may be implemented as a part of another functionally related component (e.g., a camera module (180) or a communication module (190)). In one embodiment, the auxiliary processor (123) (e.g., a neural network processing unit) may include a hardware structure specialized for processing artificial intelligence models. The artificial intelligence models may be generated through machine learning. This learning can be performed, for example, on the electronic device (101) itself where the artificial intelligence model is executed, or can be performed through a separate server (e.g., server (108)). The learning algorithm can include, for example, supervised learning, unsupervised learning, semi-supervised learning, or reinforcement learning, but is not limited to the examples described above. The artificial intelligence model can include multiple artificial neural network layers.The artificial neural network may be one of a deep neural network (DNN), a convolutional neural network (CNN), a recurrent neural network (RNN), a restricted Boltzmann machine (RBM), a deep belief network (DBN), a bidirectional recurrent deep neural network (BRDNN), a deep Q-network, or a combination of two or more of the above, but is not limited to the examples described above. In addition to, or alternatively to, a hardware structure, an artificial intelligence model may include a software structure.

[0029] The memory (130) can store various data used by at least one component (e.g., processor (120) or sensor module (176)) of the electronic device (101). The data can include, for example, software (e.g., program (140)) and input data or output data for commands related thereto. The memory (130) can include volatile memory (132) or non-volatile memory (134).

[0030] The program (140) may be stored as software in memory (130) and may include, for example, an operating system (142), middleware (144), or an application (146).

[0031] The input module (150) can receive commands or data to be used in a component of the electronic device (101) (e.g., a processor (120)) from an external source (e.g., a user) of the electronic device (101). The input module (150) can include, for example, a microphone, a mouse, a keyboard, a key (e.g., a button), or a digital pen (e.g., a stylus pen).

[0032] The audio output module (155) can output audio signals to the outside of the electronic device (101). The audio output module (155) can include, for example, a speaker or a receiver. The speaker can be used for general purposes, such as multimedia playback or recording playback. The receiver can be used to receive incoming calls. In one embodiment, the receiver can be implemented separately from the speaker or as part of the speaker.

[0033] The display module (160) can visually provide information to an external party (e.g., a user) of the electronic device (101). The display module (160) may include, for example, a display, a holographic device, or a projector and a control circuit for controlling the device. According to one embodiment, the display module (160) may include a touch sensor configured to detect a touch, or a pressure sensor configured to measure the intensity of a force generated by the touch.

[0034] The audio module (170) can convert sound into an electrical signal, or vice versa, convert an electrical signal into sound. According to one embodiment, the audio module (170) can acquire sound through the input module (150), output sound through the sound output module (155), or an external electronic device (e.g., electronic device (102)) (e.g., speaker or headphone) directly or wirelessly connected to the electronic device (101).

[0035] The sensor module (176) can detect the operating status (e.g., power or temperature) of the electronic device (101) or the external environmental status (e.g., user status) and generate an electrical signal or data value corresponding to the detected status. According to one embodiment, the sensor module (176) can include, for example, a gesture sensor, a gyro sensor, a barometric pressure sensor, a magnetic sensor, an acceleration sensor, a grip sensor, a proximity sensor, a color sensor, an IR (infrared) sensor, a biometric sensor, a temperature sensor, a humidity sensor, or an illuminance sensor.

[0036] The interface (177) may support one or more designated protocols that may be used to directly or wirelessly connect the electronic device (101) with an external electronic device (e.g., the electronic device (102)). In one embodiment, the interface (177) may include, for example, a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, an SD card interface, or an audio interface.

[0037] The connection terminal (178) may include a connector through which the electronic device (101) may be physically connected to an external electronic device (e.g., electronic device (102)). According to one embodiment, the connection terminal (178) may include, for example, an HDMI connector, a USB connector, an SD card connector, or an audio connector (e.g., a headphone connector).

[0038] The haptic module (179) can convert electrical signals into mechanical stimuli (e.g., vibration or movement) or electrical stimuli that a user can perceive through tactile or kinesthetic sensations. According to one embodiment, the haptic module (179) can include, for example, a motor, a piezoelectric element, or an electrical stimulation device.

[0039] The camera module (180) can capture still images and videos. According to one embodiment, the camera module (180) may include one or more lenses, image sensors, image signal processors, or flashes.

[0040] The power management module (188) can manage power supplied to the electronic device (101). According to one embodiment, the power management module (188) can be implemented as, for example, at least a part of a power management integrated circuit (PMIC).

[0041] A battery (189) may power at least one component of the electronic device (101). In one embodiment, the battery (189) may include, for example, a non-rechargeable primary battery, a rechargeable secondary battery, or a fuel cell.

[0042] The communication module (190) may support the establishment of a direct (e.g., wired) communication channel or a wireless communication channel between the electronic device (101) and an external electronic device (e.g., electronic device (102), electronic device (104), or server (108)), and the performance of communication through the established communication channel. The communication module (190) may operate independently from the processor (120) (e.g., application processor) and may include one or more communication processors that support direct (e.g., wired) communication or wireless communication. According to one embodiment, the communication module (190) may include a wireless communication module (192) (e.g., a cellular communication module, a short-range wireless communication module, or a global navigation satellite system (GNSS) communication module) or a wired communication module (194) (e.g., a local area network (LAN) communication module, or a power line communication module). Among these communication modules, the corresponding communication module can communicate with an external electronic device (104) via a first network (198) (e.g., a short-range communication network such as Bluetooth, wireless fidelity (WiFi) direct, or infrared data association (IrDA)) or a second network (199) (e.g., a long-range communication network such as a legacy cellular network, a 5G network, a next-generation communication network, the Internet, or a computer network (e.g., a LAN or WAN)). These various types of communication modules can be integrated into a single component (e.g., a single chip) or implemented as multiple separate components (e.g., multiple chips). The wireless communication module (192) can verify or authenticate the electronic device (101) within a communication network such as the first network (198) or the second network (199) by using subscriber information (e.g., an international mobile subscriber identity (IMSI)) stored in the subscriber identification module (196).

[0043] The wireless communication module (192) can support 5G networks and next-generation communication technologies following the 4G network, such as NR access technology (new radio access technology). The NR access technology can support high-speed transmission of high-capacity data (eMBB (enhanced mobile broadband)), minimization of terminal power and connection of multiple terminals (mMTC (massive machine type communications)), or high reliability and low latency (URLLC (ultra-reliable and low-latency communications)). The wireless communication module (192) can support, for example, a high-frequency band (e.g., mmWave band) to achieve a high data transmission rate. The wireless communication module (192) can support various technologies for securing performance in a high-frequency band, such as beamforming, massive multiple-input and multiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beam-forming, or large scale antenna. The wireless communication module (192) can support various requirements specified in the electronic device (101), an external electronic device (e.g., the electronic device (104)), or a network system (e.g., the second network (199)). According to one embodiment, the wireless communication module (192) can support a peak data rate (e.g., 20 Gbps or more) for eMBB realization, a loss coverage (e.g., 164 dB or less) for mMTC realization, or a U-plane latency (e.g., 0.5 ms or less for downlink (DL) and uplink (UL), or 1 ms or less for round trip) for URLLC realization.

[0044] The antenna module (197) can transmit or receive signals or power to or from an external device (e.g., an external electronic device). In one embodiment, the antenna module (197) may include an antenna including a radiator formed of a conductor or a conductive pattern formed on a substrate (e.g., a PCB). In one embodiment, the antenna module (197) may include a plurality of antennas (e.g., an array antenna). In this case, at least one antenna suitable for a communication method used in a communication network, such as the first network (198) or the second network (199), may be selected from the plurality of antennas, for example, by the communication module (190). A signal or power may be transmitted or received between the communication module (190) and an external electronic device via the at least one selected antenna. In some embodiments, in addition to the radiator, another component (e.g., a radio frequency integrated circuit (RFIC)) may be additionally formed as a part of the antenna module (197).

[0045] According to various embodiments, the antenna module (197) may form a mmWave antenna module. In one embodiment, the mmWave antenna module may include a printed circuit board, an RFIC disposed on or adjacent a first side (e.g., a bottom side) of the printed circuit board and capable of supporting a designated high-frequency band (e.g., a mmWave band), and a plurality of antennas (e.g., an array antenna) disposed on or adjacent a second side (e.g., a top side or a side side) of the printed circuit board and capable of transmitting or receiving signals in the designated high-frequency band.

[0046] At least some of the above components can be interconnected and exchange signals (e.g., commands or data) with each other via a communication method between peripheral devices (e.g., a bus, GPIO (general purpose input and output), SPI (serial peripheral interface), or MIPI (mobile industry processor interface)).

[0047] According to one embodiment, commands or data may be transmitted or received between the electronic device (101) and an external electronic device (104) via a server (108) connected to a second network (199). Each of the external electronic devices (102 or 104) may be the same or a different type of device as the electronic device (101). According to one embodiment, all or part of the operations executed in the electronic device (101) may be executed in one or more of the external electronic devices (102, 104, or 108). For example, when the electronic device (101) is to perform a certain function or service automatically or in response to a request from a user or another device, the electronic device (101) may, instead of or in addition to executing the function or service itself, request one or more external electronic devices to perform the function or at least a part of the service. One or more external electronic devices that receive the request may execute at least a portion of the requested function or service, or an additional function or service related to the request, and transmit the result of the execution to the electronic device (101). The electronic device (101) may process the result as is or additionally and provide it as at least a portion of a response to the request. For this purpose, cloud computing, distributed computing, mobile edge computing (MEC), or client-server computing technology may be used, for example. The electronic device (101) may provide an ultra-low latency service by using distributed computing or mobile edge computing, for example. In another embodiment, the external electronic device (104) may include an Internet of Things (IoT) device. The server (108) may be an intelligent server utilizing machine learning and / or a neural network. According to one embodiment, the external electronic device (104) or the server (108) may be included in the second network (199).The electronic device (101) can be applied to intelligent services (e.g., smart home, smart city, smart car, or healthcare) based on 5G communication technology and IoT-related technology.

[0048] FIG. 2A is a block diagram (200) of an electronic device (101) for supporting legacy network communication and 5G network communication according to various embodiments.

[0049] Referring to FIG. 2A, the electronic device (101) may include a first communication processor (212), a second communication processor (214), a first radio frequency integrated circuit (RFIC) (222), a second RFIC (224), a third RFIC (226), a fourth RFIC (228), a first radio frequency front end (RFFE) (232), a second RFFE (234), a first antenna module (242), a second antenna module (244), a third antenna module (246), and antennas (248). The electronic device (101) may further include a processor (120) and a memory (130).

[0050] The second network (199) may include a first cellular network (292) and a second cellular network (294). According to another embodiment, the electronic device (101) may further include at least one of the components described in FIG. 1, and the second network (199) may further include at least one other network. According to one embodiment, the first communication processor (212), the second communication processor (214), the first RFIC (222), the second RFIC (224), the fourth RFIC (228), the first RFFE (232), and the second RFFE (234) may form at least a portion of the wireless communication module (192). According to another embodiment, the fourth RFIC (228) may be omitted or may be included as a part of the third RFIC (226).

[0051] The first communication processor (212) may establish a communication channel in a band to be used for wireless communication with the first cellular network (292), and may support legacy network communication through the established communication channel. According to various embodiments, the first cellular network may be a legacy network including a second generation (2G), 3G, 4G, or long term evolution (LTE) network. The second communication processor (214) may establish a communication channel corresponding to a designated band (e.g., about 6 GHz to about 60 GHz) among the bands to be used for wireless communication with the second cellular network (294), and may support 5G network communication through the established communication channel. According to various embodiments, the second cellular network (294) may be a 5G network or a 6G network defined by 3GPP. Additionally, according to one embodiment, the first communication processor (212) or the second communication processor (214) may support establishment of a communication channel corresponding to another designated band (e.g., about 6 GHz or less) among the bands to be used for wireless communication with the second cellular network (294), and 5G network communication through the established communication channel.

[0052] The first communication processor (212) can transmit and receive data with the second communication processor (214). For example, data classified to be transmitted via the second cellular network (294) may be changed to be transmitted via the first cellular network (292). In this case, the first communication processor (212) can receive the transmission data from the second communication processor (214). For example, the first communication processor (212) can transmit and receive data with the second communication processor (214) via the processor-to-processor interface (213). The above interprocessor interface (213) may be implemented as, for example, a universal asynchronous receiver / transmitter (UART) (e.g., HS-UART (high speed-UART) or PCIe (peripheral component interconnect bus express) interface), but there is no limitation on its type. Alternatively, the first communication processor (212) and the second communication processor (214) may exchange control information and packet data information using, for example, a shared memory. The first communication processor (212) may transmit and receive various information, such as sensing information, information on output intensity, and resource block (RB) allocation information, with the second communication processor (214).

[0053] Depending on the implementation, the first communication processor (212) may not be directly connected to the second communication processor (214). In this case, the first communication processor (212) may transmit and receive data with the second communication processor (214) through the processor (120) (e.g., application processor). For example, the first communication processor (212) and the second communication processor (214) may transmit and receive data with the processor (120) (e.g., application processor) through an HS-UART interface or a PCIe interface, but there is no limitation on the type of interface. Alternatively, the first communication processor (212) and the second communication processor (214) may exchange control information and packet data information with the processor (120) (e.g., application processor) using shared memory.

[0054] According to one embodiment, the first communication processor (212) and the second communication processor (214) may be implemented within a single chip or a single package. According to various embodiments, the first communication processor (212) or the second communication processor (214) may be formed within a single chip or a single package with the processor (120), the auxiliary processor (123), or the communication module (190).

[0055] For example, as in FIG. 2b, the integrated communication processor (260) may support functions for communicating with both the first cellular network (292) and the second cellular network (294).

[0056] The first RFIC (222) may, upon transmission, convert a baseband signal generated by the first communication processor (212) into a radio frequency (RF) signal of about 700 MHz to about 3 GHz used in a first cellular network (292) (e.g., a legacy network). Upon reception, the RF signal may be acquired from the first network (292) (e.g., a legacy network) via an antenna (e.g., the first antenna module (242)) and preprocessed via an RFFE (e.g., the first RFFE (232)). The first RFIC (222) may convert the preprocessed RF signal into a baseband signal so that it may be processed by the first communication processor (212).

[0057] The second RFIC (224) may, upon transmission, convert a baseband signal generated by the first communication processor (212) or the second communication processor (214) into an RF signal (hereinafter, a 5G Sub6 RF signal) of a Sub6 band (e.g., about 6 GHz or less) used in the second cellular network (294) (e.g., a 5G network). Upon reception, the 5G Sub6 RF signal may be acquired from the second cellular network (294) (e.g., a 5G network) via an antenna (e.g., the second antenna module (244)) and preprocessed via an RFFE (e.g., the second RFFE (234)). The second RFIC (224) may convert the preprocessed 5G Sub6 RF signal into a baseband signal so that the preprocessed 5G Sub6 RF signal may be processed by a corresponding communication processor among the first communication processor (212) or the second communication processor (214).

[0058] The third RFIC (226) can convert the baseband signal generated by the second communication processor (214) into an RF signal (hereinafter, 5G Above6 RF signal) of a 5G Above6 band (e.g., about 6 GHz to about 60 GHz) to be used in the second cellular network (294) (e.g., 5G network). Upon reception, the 5G Above6 RF signal can be acquired from the second cellular network (294) (e.g., 5G network) through an antenna (e.g., antenna (248)) and preprocessed through the third RFFE (236). The third RFIC (226) can convert the preprocessed 5G Above6 RF signal into a baseband signal so that it can be processed by the second communication processor (214). According to one embodiment, the third RFFE (236) can be formed as a part of the third RFIC (226).

[0059] The electronic device (101) may, according to one embodiment, include a fourth RFIC (228) separately from or at least as a part of the third RFIC (226). In this case, the fourth RFIC (228) may convert a baseband signal generated by the second communication processor (214) into an RF signal (hereinafter, referred to as an IF signal) of an intermediate frequency band (e.g., about 9 GHz to about 11 GHz) and then transmit the IF signal to the third RFIC (226). The third RFIC (226) may convert the IF signal into a 5G Above6 RF signal. Upon reception, the 5G Above6 RF signal may be received from the second cellular network (294) (e.g., a 5G network) via an antenna (e.g., antenna (248)) and converted into an IF signal by the third RFIC (226). The fourth RFIC (228) can convert the IF signal into a baseband signal so that the second communication processor (214) can process it.

[0060] According to one embodiment, the first RFIC (222) and the second RFIC (224) may be implemented as a single chip or at least a portion of a single package. According to various embodiments, when the first RFIC (222) and the second RFIC (224) are implemented as a single chip or a single package in FIG. 2A or FIG. 2B, they may be implemented as an integrated RFIC (223) as illustrated in FIG. 2C. In this case, the integrated RFIC (223) may be connected to the first RFFE (232) and the second RFFE (234), such that the integrated RFIC (223) may convert a baseband signal into a signal in a band supported by the first RFFE (232) and / or the second RFFE (234), and transmit the converted signal to one of the first RFFE (232) and the second RFFE (234). According to one embodiment, the first RFFE (232) and the second RFFE (234) may be implemented as at least a portion of a single chip or a single package. According to one embodiment, at least one antenna module among the first antenna module (242) or the second antenna module (244) may be omitted or combined with another antenna module to process RF signals of a corresponding plurality of bands.

[0061] According to one embodiment, the third RFIC (226) and the antenna (248) may be disposed on the same substrate to form a third antenna module (246). For example, the wireless communication module (192) or the processor (120) may be disposed on the first substrate (e.g., the main PCB). In this case, the third RFIC (226) may be disposed on a portion (e.g., the bottom surface) of a second substrate (e.g., the sub PCB) separate from the first substrate, and the antenna (248) may be disposed on another portion (e.g., the top surface) to form the third antenna module (246). By disposing the third RFIC (226) and the antenna (248) on the same substrate, it is possible to reduce the length of the transmission line therebetween. This can reduce, for example, the loss (e.g., attenuation) of signals in a high-frequency band (e.g., about 6 GHz to about 60 GHz) used in 5G network communications by the transmission line. Due to this, the electronic device (101) can improve the quality or speed of communication with the second network (294) (e.g., 5G network).

[0062] According to one embodiment, the antenna (248) may be formed as an antenna array including a plurality of antenna elements that may be used for beamforming. In this case, the third RFIC (226) may include a plurality of phase shifters (238) corresponding to the plurality of antenna elements, for example, as part of the third RFFE (236). Upon transmission, each of the plurality of phase shifters (238) may shift the phase of a 5G Above6 RF signal to be transmitted to an external source (e.g., a base station of a 5G network) of the electronic device (101) via its corresponding antenna element. Upon reception, each of the plurality of phase shifters (238) may shift the phase of a 5G Above6 RF signal received from the external source via its corresponding antenna element to the same or substantially the same phase. This enables transmission or reception via beamforming between the electronic device (101) and the external source.

[0063] The second cellular network (294) (e.g., a 5G network) may operate independently (e.g., Stand-Alone (SA)) or in connection with (e.g., Non-Stand Alone (NSA)) the first cellular network (292) (e.g., a legacy network). For example, the 5G network may only have an access network (e.g., a 5G radio access network (RAN) or next generation RAN (NG RAN)) and no core network (e.g., next generation core (NGC)). In this case, the electronic device (101) may access an external network (e.g., the Internet) under the control of the core network (e.g., evolved packed core (EPC)) of the legacy network after accessing the access network of the 5G network. Protocol information for communication with a legacy network (e.g., LTE protocol information) or protocol information for communication with a 5G network (e.g., New Radio (NR) protocol information) may be stored in the memory (130) and accessed by other components (e.g., the processor (120), the first communication processor (212), or the second communication processor (214)).

[0064] The present disclosure proposes embodiments for improving the reception performance of a Multiple-Input Multiple-Output (MIMO) system based on Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). For a specific description of the receiver operation according to the embodiments of the present disclosure, a plurality (e.g., N) t ) and multiple transmitting antenna ports (e.g., N rAssume a MIMO-OFDM or MIMO-OFDMA communication system using the receiving antenna ports of a dog.

[0065] FIG. 3 is a diagram illustrating the concept of a resource block, which is the minimum unit to which a receiving method according to one embodiment of the present disclosure is applied.

[0066] A resource block considered in this embodiment may be composed of K adjacent subcarriers on the frequency axis and N adjacent OFDM symbols on the time axis. According to one embodiment, a resource block may use a fixed value according to the subcarrier spacing, and may also be a unit that is adaptively set according to the time-domain correlation and the frequency-domain correlation of the channel. For example, a resource block may be composed of 12 subcarriers and 14 OFDM symbols, in which case k=12 and N=14. In this embodiment, for convenience of explanation, the k-th subcarrier of the n-th OFDM symbol in a resource block is defined as the (n, k)-th resource element. According to this definition, each resource block may be composed of NK resource elements.

[0067] According to one embodiment, a MIMO-OFDM system with Code Division Multiplexing (CDM) may be considered. When the number of CDM groups is J, N t The transmit antenna ports of the n-th resource element are assigned to one of the J CDM groups. When code division multiplexing is applied, the channel matrix of the (n, k)-th resource element can be expressed as in Equation 1.

[0068] [Mathematical Formula 1]

[0069]

[0070] Here For the (n,k)th resource element, the transmit antenna ports belonging to the jth CDM group and N ris a channel matrix formed between the receiving antenna ports of the receiver. In order to estimate the channel of each CDM group, it is assumed that demodulation reference signals (DM-RSs) already known to the receiver are transmitted through D resource elements among the resource elements in the resource block. In particular, the i-th DM-RS transmitted for the j-th CDM group channel estimation is It is assumed that the DM-RS transmitted at this time is transmitted through the th resource element. It is expressed as . N of t All signals transmitted from the transmit antenna ports that do not belong to the jth CDM group among the elements have a zero value. In this case, Received signal observed at the th resource element can be expressed as in mathematical formula 2.

[0071] [Equation 2]

[0072]

[0073] Here, represents the noise signal received at the (n,k)th resource element, represents the interference signal received at the (n,k)th resource element.

[0074] In this embodiment, it is assumed that data symbols are transmitted through the remaining resource elements in the resource block in which DM-RS is not transmitted. The data symbol transmitted through the (n,k)th resource element is x[n,k]= can be expressed as . Here, A represents the symbol constellation shared in advance by the transmitter and receiver. The received signal observed through the (n,k)th resource element where the data symbol is transmitted can be expressed as in mathematical formula 3.

[0075] [Equation 3]

[0076]

[0077] Here, represents the frequency domain channel matrix formed for the kth subcarrier of the nth OFDM symbol, represents the noise signal observed in the kth subcarrier of the nth OFDM symbol.

[0078] FIG. 4 is a diagram showing an example of a basic unit of time and frequency resources constituting a downlink control channel according to one embodiment of the present disclosure.

[0079] According to FIG. 4, the basic unit of time and frequency resources (Resource Element Group: REG) constituting the control channel can be composed of 1 OFDM symbol (401) in the time axis and 12 subcarriers (402), i.e., 1 RB, in the frequency axis. By assuming that the basic unit of the time axis is 1 OFDM symbol (401) in constituting the basic unit of the control channel, the data channel and the control channel can be time multiplexed within one subframe. By positioning the control channel before the data channel, the processing time of the user can be reduced, making it easy to satisfy the delay time requirement. By setting the basic unit of the frequency axis of the control channel to 1 RB, frequency multiplexing between the control channel and the data channel can be performed more efficiently.

[0080] By concatenating REGs (403) illustrated in FIG. 4, control channel regions of various sizes can be set. For example, if the basic unit to which a downlink control channel is allocated in 5G is called CCE (404), 1 CCE (404) can be composed of multiple REGs (403). Taking REG (404) illustrated in FIG. 4 as an example, if REG (403) can be composed of 12 REs and 1 CCE (404) is composed of 6 REGs (403), it means that 1 CCE (404) can be composed of 72 REs. When a downlink control region is set, the region can be composed of multiple CCEs (404), and a specific downlink control channel can be mapped to one or multiple CCEs (404) and transmitted according to the aggregation level (AL) within the control region. CCEs (404) within the control area are distinguished by numbers, and the numbers can be assigned according to a logical mapping method.

[0081] The basic unit of the downlink control channel illustrated in FIG. 4, that is, the REG (403), may include both the REs to which the DCI is mapped and the area to which the DMRS (Demodulation Reference Signal, 405), which is a reference signal for decoding the REs, is mapped. As shown in FIG. 4, the DMRS (405) may be transmitted in six REs within one REG (403). For reference, since the DMRS (403) is transmitted using the same precoding as the control signal mapped within the REG (403), the terminal can decode the control information even without information on what precoding the base station applied.

[0082] FIG. 5 is a diagram illustrating an example of a configuration for a downlink RB structure according to one embodiment of the present disclosure.

[0083] When a specific terminal is scheduled for a data channel, i.e., a physical uplink shared channel (PUSCH) or a physical downlink shared channel (PDSCH) via a physical downlink control channel (PDCCH), data can be transmitted and received together with DMRS within the scheduled resource region. Figure 5 illustrates a case where a specific terminal uses 14 OFDM symbols as one slot (or subframe) in the downlink, the PDCCH is transmitted in the first two OFDM symbols, and the DMRS is transmitted in the third symbol.

[0084] In the case of Fig. 5, within a specific RB where the PDSCH is scheduled, the PDSCH can be transmitted by mapping data to REs where DMRS is not transmitted in the third symbol and REs from the fourth to the last symbol thereafter. The subcarrier spacing expressed in Fig. 5 f is 15 kHz for LTE / LTE-A systems and one of {15, 30, 60, 120, 240, 480} kHz can be used for 5G systems.

[0085] Meanwhile, as described above, in order to measure the downlink channel status in a cellular system, the base station can transmit a reference signal. In the case of the 3GPP LTE-A (Long Term Evolution Advanced) system, the terminal can measure the channel status between the base station and the terminal using the CRS or CSI-RS transmitted by the base station. The channel status must be measured by considering various factors, which may include the amount of interference in the downlink. The amount of interference in the downlink includes interference signals and thermal noise generated by antennas belonging to adjacent base stations, and the amount of interference in the downlink is important for the terminal to determine the channel status of the downlink. For example, when a signal is transmitted from a base station using one transmitting antenna to a terminal using one receiving antenna, the terminal can determine Es / Io by judging the energy per symbol (Es) that can be received in the downlink from the reference signal received from the base station and the amount of interference (Io) that will be simultaneously received in the section in which the corresponding symbol is received. The determined Es / Io is converted into a data transmission rate or a value corresponding thereto and transmitted to the base station in the form of a channel quality indicator (CQI), which can be used by the base station to determine at what data transmission rate to perform transmission to the terminal.

[0086] In the LTE-A system, the terminal feeds back information about the downlink channel status to the base station, allowing it to be utilized in the base station's downlink scheduling. Specifically, the terminal measures the reference signal transmitted by the base station on the downlink and feeds back the extracted information to the base station in a format defined by the LTE / LTE-A standard. As described above, the information fed back by the terminal in LTE / LTE-A can be referred to as channel status information, and this channel status information can include the following three types of information.

[0087] - Rank Indicator (RI): The number of spatial layers that the terminal can receive in the current channel state.

[0088] - Precoding Matrix Indicator (PMI): An indicator of the precoding matrix preferred by the terminal in the current channel condition.

[0089] - Channel Quality Indicator (CQI): The maximum data rate that the terminal can receive in the current channel condition.

[0090] CQI can also be replaced by signal-to-interference plus noise ratio (SINR), maximum error correction code rate and modulation scheme, and data efficiency per frequency, which can be utilized similarly to maximum data rate.

[0091] The above RI, PMI, and CQI are interrelated and have different meanings. For example, the precoding matrix supported by LTE / LTE-A is defined differently for each rank. For example, the PMI value X when RI has a value of 1 and the PMI value X when RI has a value of 2 may be interpreted differently. In addition, when the terminal determines the CQI, it is assumed that the PMI value X that the terminal notified to the base station is applied by the base station. In other words, when the terminal reports RI_X, PMI_Y, and CQI_Z to the base station, it is the same as reporting that the terminal can receive the data rate corresponding to CQI_Z when the rank is RI_X and the PMI is PMI_Y. In this way, when the terminal calculates the CQI, it assumes which transmission method the base station will perform so that it can obtain optimized performance when actually performing transmission with the corresponding transmission method.

[0092] The channel state information (RI, PMI, CQI) fed back by the terminal can be fed back in a periodic or aperiodic form. If the base station wishes to aperiodically acquire the channel state information of a specific terminal, the base station can configure to perform aperiodic feedback (or aperiodic channel state information reporting) using an aperiodic feedback indicator (or channel state information request field, channel state information request information) included in the downlink control information (DCI) for the terminal. In addition, if the terminal receives an indicator configured to perform aperiodic feedback in the nth subframe, the terminal can perform uplink transmission by including the aperiodic feedback information (or channel state information) in the data transmission in the (n+k)th subframe. Here, k is a parameter defined in the 3GPP LTE Release 11 standard, for example, and can be 4 in FDD (Frequency Division Duplexing).

[0093] FIG. 6a is a diagram showing an example of an MU-MIMO environment in a wireless communication system according to an embodiment of the present disclosure, and FIG. 6b is a diagram showing an example of an SU-MIMO environment in a wireless communication system according to an embodiment of the present disclosure.

[0094] Referring to Fig. 6a, M in the downlink of a wireless communication system t A base station (61) using multiple antennas and an M using at least one receiving antenna r A DL MU (multi-user)-MIMO environment including UEs (62, 63, 64) can be implemented. In the uplink of a wireless communication system, M r A base station (61) using multiple antennas and an M using at least one transmitting antenna r A UL MU-MIMO environment including UEs (62, 63, 64) can be implemented.

[0095] Referring to Fig. 6b, M in the downlink of a wireless communication system t Base station (61) using multiple antennas and M r It can also be applied to a DL SU (single user)-MIMO environment including one UE (65) using a receiving antenna. In the uplink of a wireless communication system, M t Base station (61) using multiple antennas and M r It can also be applied to a UL SU-MIMO environment including one UE (65) using a dog's transmit antenna.

[0096] Embodiments of the present disclosure can be applied to a MIMO environment in which the number of transmit / receive antennas of a base station and the number of transmit / receive antennas of a terminal are implemented in various ways.

[0097] FIG. 7 is a block diagram showing in detail the process of executing a receiving method of a MIMO-OFDM communication system according to one embodiment of the present disclosure.

[0098] For convenience of explanation, in this embodiment, it is assumed that all operations shown in FIG. 7 are applied to resource block units of FIG. 3. However, the resource block units of FIG. 3 are freely defined depending on the implementation, and the embodiments of the present disclosure can also be applied to resource block units implemented in various ways.

[0099] Referring to FIG. 7, the electronic device may include a common channel estimation unit (710), a port-reduction filter design unit (720), an interference covariance estimation unit (730), a channel equalization unit (740), and a channel decoding unit (760). According to one embodiment, the electronic device may further include a common channel re-estimation unit (750). According to one embodiment, the electronic device of FIG. 7 may be implemented as a base station and / or a UE.

[0100] The common channel estimation unit (710) can determine a common channel estimate representing the entire resource block. To this end, the common channel estimation unit (710) can first determine channel estimates for resource elements to which DM-RSs are allocated within the resource block. According to one embodiment, the common channel estimation unit (710) can group adjacent DM-RSs among D DM-RSs to estimate a channel of a resource element representing the group in order to determine channel estimates of resource elements to which DM-RSs are allocated. According to one embodiment, when the resource element representing a specific DM-RS group is the (n, k)th resource element, when the least squares technique is used, the channel estimate of the (n, k)th resource element can be expressed as in Equation 4.

[0101] [Equation 4]

[0102]

[0103] Here, is a matrix whose rows are DM-RSs used to estimate the channel of the (n,k)th resource element in the jth CDM group, is a matrix whose rows are the received signals of the DM-RSs used to estimate the channel of the (n,k)th resource element in the jth CDM group. In addition, represents the Hermitian operation, represents the inverse matrix operation. By concatenating the channel estimates obtained for each CDM group, the channel estimate for the (n, k)th resource element can be expressed as in mathematical expression 5.

[0104] [Equation 5]

[0105]

[0106] The common channel estimate representing a resource block can be determined as the average of the channel estimates for the resource elements to which DM-RSs are assigned within the resource block. In this case, the common channel estimate representing the resource block can be expressed as in Equation 6.

[0107] [Equation 6]

[0108]

[0109] Here, R is the index set of resource elements in which DM-RS is transmitted within the resource block, represents the size of the set R. Common channel estimate In addition to the least squares technique mentioned above, it can be defined by utilizing or applying various estimation techniques.

[0110] The port reduction filter design unit (720) determines the common channel estimate value determined by the common channel estimation unit (710). Based on , the dimension of the received signal is M (where M <N r ) can be determined for reducing the linear filter. As an example of a linear filter determination method, Maximal Ratio Combining (MRC) can be considered. By applying the MRC method, a linear filter can be obtained as in mathematical expression 7.

[0111] [Equation 7]

[0112]

[0113] The linear filter obtained through the maximum ratio combining method is M=N t The condition is satisfied. Therefore, if the above linear filter is used, N t <N r In this situation, the dimension of the received signal can be reduced. M>N t In this case, a linear filter decision method other than the maximum ratio combining method can be considered. To improve performance, the common channel re-estimation value determined in the common channel re-estimation (750) section of Fig. 7 It is also possible to determine a linear filter using .

[0114] The linear filter (W) determined through the port reduction filter design unit (720) is a received signal for DM-RS. and received signals for data It can be used to reduce the dimension of. The received signals that have passed through the linear filter can be expressed as in Equations 8 and 9, respectively.

[0115] [Equation 8]

[0116]

[0117] [Equation 9]

[0118]

[0119] Referring to mathematical expressions 8 and 9, the received signals after passing through the linear filter (W) have the dimension of the original received signal, N r It can be expressed as a reduced M-dimensional vector. The dimensionality reduction of the received signal can reduce the computational complexity of the subsequent interference covariance matrix estimation and channel equalization processes. The method of reducing the computational complexity of the receiving process using a linear filter according to the above embodiment is one of the key features of the proposed receiving method.

[0120] In this disclosure, a dimensionally reduced reception signal can be defined as a valid reception signal. The valid reception signal for the (n, k)th resource element is the existing channel. This is not a valid channel . The estimate for the effective channel is the common channel estimate determined by the common channel estimation unit (710) using the linear filter (W) determined by the port reduction filter design unit (720). It can be expressed by multiplying by . In this case, the effective channel estimate (G) can be expressed as follows.

[0121] [Equation 10]

[0122]

[0123] The effective channel estimate (G) determined by the above method can replace the channel estimate of the existing technique in the subsequent interference covariance matrix estimation and channel equalization processes.

[0124] The interference covariance estimation unit (730) can determine the covariance matrix estimate of the interference signal based on the effective channel estimate (G) determined by the port reduction filter design unit (720). The effective received signal for the (n, k)th resource element where the DM-RS is transmitted The signal obtained by multiplying the effective channel estimate (G) by the DM-RS and removing the signal is the effective interference signal. can be defined as follows. If the common channel estimate for the resource elements within the resource block is sufficiently similar to the actual channel, Equation 11 can be established.

[0125] [Equation 11]

[0126]

[0127] If the above formula is established, the effective interference signal for the (n,k)th resource element where the DM-RS is transmitted can be expressed as in mathematical formula 12.

[0128] [Equation 12]

[0129]

[0130] The covariance matrix estimate of an interference signal can be determined using valid interference signals corresponding to resource elements within a resource block on which a DM-RS is transmitted. For example, the covariance matrix of an interference signal can be estimated as in Equation 13.

[0131] [Equation 13]

[0132]

[0133] In the process of determining the interference covariance matrix estimate, the M-dimensional effective interference signal It only uses the existing N r Dimensional reception signal ) has the advantage of lower computational complexity compared to the method using .

[0134] The channel equalization unit (740) can perform channel equalization based on the interference covariance estimation value (C) determined by the interference covariance estimation unit (730) and the effective channel estimation value (G) determined by the port reduction filter design unit (720). For example, in the case of channel equalization utilizing the linear least mean square error technique, the data estimation value for the (n, k)th resource element can be expressed as in mathematical expression 14.

[0135] [Equation 14]

[0136]

[0137] For example, in the case of channel equalization using the least squares technique, the data estimate for the (n,k)th resource element can be expressed as in Equation 15.

[0138] [Equation 15]

[0139]

[0140] In the channel equalization unit (740) according to the proposed receiving method, the channel estimation value It has the characteristic of determining the same channel equalizer for all resource elements within a resource block by utilizing the effective channel estimate (G) rather than the resource block. Due to this characteristic, there is no need to determine a separate channel equalizer for each resource element, which can reduce the computational complexity proportional to the number of resource elements within the resource block. In addition, Instead of channel estimates of dimension By utilizing the effective channel estimates of the dimension, the computational complexity required to determine the channel equalizer can also be reduced. Unlike the proposed method, existing techniques use a channel estimate for each resource element. , a separate channel equalizer is determined, which inevitably leads to high computational complexity.

[0141] The channel decoder (760) can recover data bits based on the data estimates determined by the channel equalizer (740). To this end, the channel decoder (760) can calculate the log-likelihood ratio (LLR) for each bit based on the data estimates.

[0142] The common channel re-estimation unit (750) estimates the common channel based on the data estimates determined by the channel equalization unit (740). can be re-determined. If the values ​​of the data estimates determined by the channel equalizer (740) are not expressed as one of the elements of the symbol constellation, a process of corresponding them to the nearest element among the elements of the symbol constellation may be performed first. As an example of the common channel estimate re-determination, when the least squares technique is used, the common channel re-estimation value can be expressed as in mathematical expression 16.

[0143] [Equation 16]

[0144]

[0145] Here, is a matrix having as rows the received signals for all DM-RSs within a resource block and the received signals for data signals, is a matrix with all DM-RS and data estimates within a resource block as rows. The common channel re-estimation value determined through the above process is the common channel estimate determined by the above common channel estimation unit. It is determined by utilizing a larger number of data. Due to this characteristic, the channel re-estimation value determined by the common channel re-estimation unit may have a lower channel estimation error than the channel estimate determined by the common channel estimation unit.

[0146] The common channel re-estimation unit (750) is not an essential process in the proposed receiving process, but is an optional process for improving performance through additional calculations. The electronic device can flexibly use the common channel re-estimation unit (750) depending on the computational complexity and required performance of the receiving process. When the common channel re-estimation unit (750) is selected, the port reduction filter design unit (720) uses the channel re-estimation value determined by the common channel re-estimation unit (750). The linear filter can be redesigned using this. Afterwards, the same process as the above receiving method is followed.

[0147] FIG. 8 is a diagram illustrating a receiver structure of a MIMO-OFDM communication system according to one embodiment of the present disclosure.

[0148] Referring to FIG. 8, a receiver (or receiving device) included in an electronic device may include an OFDM decoding unit (ODFM Decoding) (810), a common channel estimation unit (820), a port reduction filter unit (830), an interference covariance estimation unit (840), a channel equalization unit (850), and a channel decoding unit (860).

[0149] The OFDM decoder (810) can convert the received signal into an OFDM received signal (y[n,k]) in the time-frequency domain. The common channel estimator (820) can utilize the received signal for the DM-RS among the received signals converted by the OFDM decoder (810) for channel estimation. The common channel estimator (820) can estimate the channel through a channel estimation process based on the received signal for the DM-RS. , and determine the channel estimate The port reduction filter unit (830) can be determined using .

[0150] The linear filter (W) determined through the decision process for the port reduction filter unit (830) can be utilized for receiving signal conversion. The effective receiving signal converted through the port reduction filter unit (830) The valid received signal for the DM-RS can be utilized for interference covariance estimation in the interference covariance estimation unit (840).

[0151] Valid received signal converted through port reduction filter section (830) A valid reception signal for the medium data may undergo channel equalization in a channel equalization unit (850). The data estimate determined through the channel equalization process in the channel equalization unit (850) may be recovered into data bits through a channel decoding process in a channel decoder (860).

[0152] FIG. 9 is a flowchart showing the overall operation process of a receiving method according to one embodiment of the present disclosure.

[0153] Referring to FIG. 9, at operation 910, the electronic device may determine a common channel estimate representing channels of resource elements within a resource block using a received signal for a DM-RS. At operation 920, the electronic device may design a port reduction linear filter based on the common channel estimate. At operation 930, the electronic device may estimate an interference covariance matrix using valid signals that have passed through the designed linear filter. At operation 940, the electronic device may perform channel equalization based on the valid channel estimate and the interference covariance matrix estimate.

[0154] At step 950, the electronic device may determine whether to perform common channel re-estimation based on the requirements of the device (or system). If the electronic device determines not to perform common channel re-estimation (950-No), at step 960, the electronic device may perform channel decoding based on the data estimate to recover the information bits. If the electronic device determines to perform common channel re-estimation (950-Yes), at step 970, the electronic device may perform common channel re-estimation using the data estimate and the DM-RS. The re-estimated common channel estimate may be utilized in the design of a port reduction filter, and the same process from interference covariance estimation to channel decoding may be performed thereafter.

[0155] The receiving method of the present invention can allow multiple resource blocks to share a common channel by averaging channel estimates through demodulation reference signals within multiple resource blocks.

[0156] According to one embodiment, a method for reducing computational complexity in a linear minimum mean square error (LMMSE) channel equalizer can be performed by reducing the dimension of an effective channel and the dimension of an effective received signal from a common channel shared by a plurality of resource blocks.

[0157] According to one embodiment, a method may be performed to estimate a covariance matrix of an interference signal using a common channel, a demodulation reference signal, and a received signal, configure a channel equalizer using the same, and then re-estimate the channel based on detected data to increase the accuracy of the channel estimate, thereby improving data detection performance. The receiving method of the present invention is expected to improve receiving performance compared to conventional techniques that utilize a channel equalizer configured using only a demodulation reference signal.

[0158] According to one embodiment, a method of an electronic device for receiving a signal in an orthogonal frequency division multiplexing (OFDM) system may include an operation of determining a common channel estimate based on demodulation reference signals belonging to a resource block comprised of a plurality of adjacent OFDM symbols in a time domain and a plurality of adjacent subcarriers in a frequency domain. The method of the electronic device may include an operation of determining a port reduction filter for reducing a dimension of a received signal based on the common channel estimate. The method of the electronic device may include an operation of determining a covariance matrix based on a received signal that has passed through the port reduction filter. The method of the electronic device may include an operation of performing channel equalization based on the port reduction filter and the covariance matrix.

[0159] According to one embodiment, the electronic device may be implemented as a base station or a user equipment (UE).

[0160] In one embodiment, the operation of determining the covariance matrix may include an operation of determining a covariance matrix for a noise or interference signal using the received signal passing through the port reduction filter and the demodulation reference signals belonging to the resource block.

[0161] According to one embodiment, the method of the electronic device may further include: determining whether to perform common channel re-estimation; and, if it is determined not to perform the common channel re-estimation, performing channel decoding based on the data estimate to recover information bits.

[0162] According to one embodiment, the method of the electronic device may further include performing common channel re-estimation using the demodulation reference signals and data estimates.

[0163] In one embodiment, the channel equalization may be performed in a linear minimum mean square error (LMMSE) channel equalizer. In one embodiment, the common channel estimate may be determined as an average of channel estimates for resource elements to which the demodulation reference signals are assigned within the resource block.

[0164] According to one embodiment, a storage medium storing at least one computer-readable instruction, wherein the at least one instruction, when executed by at least a part of at least one processor (120) of an electronic device, causes the electronic device to perform at least one operation. The at least one operation may include determining a common channel estimate based on demodulation reference signals belonging to a resource block comprised of a plurality of adjacent OFDM symbols in a time domain and a plurality of adjacent subcarriers in a frequency domain. The at least one operation may include determining a port reduction filter for reducing a dimension of a received signal based on the common channel estimate. The at least one operation may include determining a covariance matrix based on a received signal that has passed through the port reduction filter. The at least one operation may include performing channel equalization based on the port reduction filter and the covariance matrix.

[0165] According to one embodiment, an electronic device may include at least one processor (120); and a memory (130) storing at least one instruction. The at least one instruction, when executed by at least a portion of the at least one processor (120), may cause the electronic device to perform at least one operation. The at least one operation may include determining a common channel estimate based on demodulation reference signals belonging to a resource block comprised of a plurality of adjacent OFDM symbols in the time domain and a plurality of adjacent subcarriers in the frequency domain. The at least one operation may include determining a port reduction filter for reducing a dimension of a received signal based on the common channel estimate. The at least one operation may include determining a covariance matrix based on a received signal passing through the port reduction filter. The at least one operation may include performing channel equalization based on the port reduction filter and the covariance matrix.

[0166] FIG. 10 and FIG. 11 are diagrams showing examples of frame error rates versus signal-to-noise ratios that can be achieved by various receiving methods according to one embodiment of the present disclosure.

[0167] Referring to FIGS. 10 and 11, the first method represents an example of a conventional method that does not perform common channel estimation as proposed in the present disclosure, the second method represents a method that performs common channel estimation as proposed in the present disclosure, the third method represents a method that performs common channel estimation and common channel re-estimation as proposed in the present disclosure, and the fourth method represents an ideal case with perfect channel information.

[0168] Figures 10 and 11 Assume an antenna configuration and 4-quadrature amplitude modulation (QAM). Also, both Figs. 10 and 11 assume a time-varying channel as in Equation 17.

[0169] [Equation 17]

[0170]

[0171] Here, represents the time-domain correlation coefficient with the previous channel, and Z[n,k] represents a complex Gaussian random matrix with the same variance as the channel. Figures 10 and 11 are Assuming that the carrier frequency is 3.5 GHz and the OFDM symbol period is In this case, the above correlation coefficient represents the case where the receiver's speed is 120 km / h.

[0172] Figures 10 and 11 illustrate examples of frame error rates versus signal-to-noise ratios that methods 1 through 4 can achieve in an environment without interference signals, using the least squares method for channel estimation and the linear least squares error method for data detection. Figure 10 illustrates examples of frame error rates versus signal-to-noise ratios that methods 1 through 4 can achieve in an environment with a signal-to-interference ratio of 0 dB.

[0173] Referring to FIG. 10, both the second method and the third method proposed in the present disclosure can provide a lower frame error rate than the first method.

[0174] Referring to FIG. 11, both the second method and the third method proposed in the present disclosure can provide a lower frame error rate than the first method in an environment where the signal-to-interference ratio is 0 dB.

[0175] The embodiments of this document and the terminology used herein are not intended to limit the technical features described in this document to specific embodiments, but should be understood to include various modifications, equivalents, or substitutes of the embodiments. In connection with the description of the drawings, similar reference numerals may be used for similar or related components. The singular form of a noun corresponding to an item may include one or more of the items, unless the context clearly indicates otherwise. In this document, each of the phrases "A or B", "at least one of A and B", "at least one of A or B", "A, B, or C", "at least one of A, B, and C", and "at least one of A, B, or C" can include any one of the items listed together in the corresponding phrase among those phrases, or all possible combinations thereof. Terms such as "first," "second," or "first" or "second" may be used merely to distinguish one component from another, and do not limit the components in any other respect (e.g., importance or order). When a component (e.g., a first component) is referred to as "coupled" or "connected" to another (e.g., a second component), with or without the terms "functionally" or "communicatively," it means that the component can be connected to the other component directly (e.g., wired), wirelessly, or through a third component.

[0176] The term "module" used in the embodiments of this document may include a unit implemented in hardware, software, or firmware, and may be used interchangeably with terms such as logic, logic block, component, or circuit. A module may be an integral component, or a minimum unit or part of such a component that performs one or more functions. For example, according to one embodiment, a module may be implemented in the form of an application-specific integrated circuit (ASIC).

[0177] One embodiment of the present document may be implemented as software (e.g., a program (140)) including one or more instructions stored in a storage medium (e.g., an internal memory (136) or an external memory (138)) readable by a machine (e.g., an electronic device (101)). For example, a processor (e.g., a processor (120)) of the machine (e.g., an electronic device (101)) may call at least one instruction among the one or more instructions stored from the storage medium and execute it. This enables the machine to operate to perform at least one function according to the at least one called instruction. The one or more instructions may include code generated by a compiler or code executable by an interpreter. The machine-readable storage medium may be provided in the form of a non-transitory storage medium. Here, 'non-transitory' simply means that the storage medium is a tangible device and does not contain signals (e.g., electromagnetic waves), and the term does not distinguish between cases where data is stored semi-permanently or temporarily on the storage medium.

[0178] According to one embodiment, the method according to one embodiment disclosed in this document may be provided as included in a computer program product. The computer program product may be traded as a product between a seller and a buyer. The computer program product may be distributed in the form of a machine-readable storage medium (e.g., compact disc read-only memory (CD-ROM)), or may be distributed online (e.g., downloaded or uploaded) via an application store (e.g., Play Store™) or directly between two user devices (e.g., smart phones). In the case of online distribution, at least a portion of the computer program product may be temporarily stored or temporarily generated in a machine-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or an intermediary server.

[0179] According to one embodiment, each component (e.g., a module or a program) of the above-described components may include one or more entities, and some of the entities may be separated and arranged in other components. According to one embodiment, one or more components or operations of the aforementioned components may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (e.g., a module or a program) may be integrated into a single component. In this case, the integrated component may perform one or more functions of each of the plurality of components identically or similarly to those performed by the corresponding component among the plurality of components prior to the integration. According to one embodiment, the operations performed by a module, program, or other component may be executed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be executed in a different order, omitted, or one or more other operations may be added.

Claims

1. A method of an electronic device receiving a signal in an OFDM (orthogonal frequency division multiplexing) system, An operation of determining a common channel estimate based on demodulation reference signals belonging to a resource block composed of a plurality of adjacent OFDM symbols in the time domain and a plurality of adjacent subcarriers in the frequency domain; An operation of determining a port reduction filter for reducing the dimensionality of a received signal based on the above common channel estimate; An operation of determining a covariance matrix based on a received signal that has passed through the above port reduction filter; and A method characterized by including an operation of performing channel equalization based on the port reduction filter and the covariance matrix.

2. In paragraph 1, A method characterized in that the electronic device is implemented as a base station or UE (user equipment).

3. In the first paragraph, the operation of determining the covariance matrix is ​​as follows: A method characterized by comprising an operation of determining a covariance matrix for a noise or interference signal using a received signal that has passed through the port reduction filter and the demodulation reference signals belonging to the resource block.

4. In paragraph 1, Actions to determine whether to perform common channel re-estimation; and A method characterized in that it further includes an operation of recovering information bits by performing channel decoding based on the data estimate when it is decided not to perform the above common channel re-estimation.

5. In paragraph 1, A method characterized by further comprising an operation of performing common channel re-estimation using the above demodulation reference signals and data estimates.

6. In paragraph 1, A method characterized in that the above channel equalization is performed in a linear minimum mean square error (LMMSE) channel equalizer.

7. A method according to claim 1, characterized in that the common channel estimate is determined as an average of channel estimates for resource elements to which the demodulation reference signals are allocated within the resource block.

8. In a storage medium storing at least one computer-readable instruction, the at least one instruction, when executed by at least a part of at least one processor (120) of an electronic device, causes the electronic device to perform at least one operation, At least one of the above actions: An operation of determining a common channel estimate based on demodulation reference signals belonging to a resource block composed of a plurality of adjacent OFDM symbols in the time domain and a plurality of adjacent subcarriers in the frequency domain; An operation of determining a port reduction filter for reducing the dimensionality of a received signal based on the above common channel estimate; An operation of determining a covariance matrix based on a received signal that has passed through the above port reduction filter; and A storage medium characterized by including an operation for performing channel equalization based on the port reduction filter and the covariance matrix.

9. In paragraph 8, A storage medium characterized in that the electronic device is implemented as a base station or UE (user equipment).

10. In the 8th paragraph, the operation of determining the covariance matrix is ​​as follows: A storage medium characterized by comprising an operation of determining a covariance matrix for a noise or interference signal using a received signal that has passed through the port reduction filter and the demodulation reference signals belonging to the resource block.

11. In paragraph 8, at least one operation: Actions to determine whether to perform common channel re-estimation; and A storage medium characterized in that it further includes an operation of recovering information bits by performing channel decoding based on the data estimate when it is decided not to perform the above common channel re-estimation.

12. In paragraph 8, at least one operation: A storage medium further comprising an operation of performing common channel re-estimation using the above demodulation reference signals and data estimates.

13. In electronic devices, at least one processor; and Contains memory that stores at least one instruction, wherein said at least one instruction, when executed by at least a portion of said at least one processor, causes said electronic device to perform at least one operation; At least one of the above actions: An operation of determining a common channel estimate based on demodulation reference signals belonging to a resource block composed of a plurality of adjacent OFDM symbols in the time domain and a plurality of adjacent subcarriers in the frequency domain; An operation of determining a port reduction filter for reducing the dimensionality of a received signal based on the above common channel estimate; An operation of determining a covariance matrix based on a received signal that has passed through the above port reduction filter; and A device characterized by including an operation for performing channel equalization based on the port reduction filter and the covariance matrix.

14. A device according to claim 13, characterized in that the electronic device is implemented as a base station or UE (user equipment).

15. In the 13th paragraph, the operation of determining the covariance matrix is: A device characterized by comprising an operation of determining a covariance matrix for a noise or interference signal using a received signal that has passed through the port reduction filter and the demodulation reference signals belonging to the resource block.

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